Abstract
Investigations are performed of the crystal structure and magnetic and electromagnetic properties of single crystals (0.23 ≤x≤0.34) and polycrystals (0 ≤x ≤0.50) of an Nd1−x BaxMnO3−δ system of solid solutions. It is found that, for samples prepared in the air, the maximal Curie temperature (T C ) does not exceed 150 K, while, in the case of polycrystalline samples in the concentration range of 0.34 ≤x ≤0.50, prepared in a reducing medium (a gaseous mixture of argon and carbon monoxide), T C increases to 320 K. As a result of the reducing medium effect on the compositions, the type of the magnetic phase transition to the paramagnetic state changes from the first to second order. The electrical resistivity of reduced polycrystalline samples (0.34≤x ≤0.50) decreases in magnitude and correlates with the behavior of magnetization. Both series of samples, prepared both in the air and in a reducing medium, exhibit a transition from the metal to dielectric state at a temperature below T C . The temperature and field dependences of magnetization for the stoichiometric polycrystalline com-position of Nd0.50Ba0.50MnO3 are measured under conditions of hydrostatic pressure. It is demonstrated that the hydrostatic pressure induces in Nd0.50Ba0.50MnO3 the transition from the antiferromagnetic to ferromagnetic state. Based on the measurement results, hypothetical magnetic phase diagrams are constructed for the system of solid solutions being treated, depending on the concentration of barium and the method of preparation. It is found that no T TC increase is observed in single crystals (0.23≤x≤0.34) such as is observed in polycrystals. It is assumed that the abrupt increase in T C of polycrystalline samples prepared in a reducing medium is a result of the emergence of extended defects and microstresses in the crystal lattice.
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Translated from Zhurnal Éksperimental’no\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\) i Teoretichesko\(\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}\) Fiziki, Vol. 121, No. 2, 2002, pp. 388–395.
Original Russian Text Copyright © 2002 by Trukhanov, Troyanchuk, Khalyavin, Fita, Szymczak, Bärner.
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Trukhanov, S.V., Troyanchuk, I.O., Khalyavin, D.D. et al. Investigation of magnetic phase transformations in a system of Nd1−x BaxMnO3−δ (0≤x≤0.50) depending on the conditions of preparation. J. Exp. Theor. Phys. 94, 329–335 (2002). https://doi.org/10.1134/1.1458482
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DOI: https://doi.org/10.1134/1.1458482